We describe the clinicopathological findings of a woman, 83 years of age at the time of death, who demonstrated dementia and numerous cerebral infarctions. She had a history of repeated mitral valve replacements 15 and 13 years prior to death and showed a dull responsive state 1 month after the second operation. Thereafter, dementia manifested and slowly progressed. Brain computed tomography revealed cortical atrophy and ventricular dilatation. Histological examination revealed a large number of minute foci of infarction in the cerebral cortex. Such lesions may have developed in association with the valve replacement and resulted in progressive dementia.